Patients have long sought retail access to cannabis, arguing the state's rules -- grow your own marijuana or have someone do it for you -- are unrealistic.

The law comes a year after an investigation by The Oregonian showed that scant state regulation of medical marijuana allowed widespread diversion to the black market. Oregon joins a dozen other states that allow medical marijuana dispensaries or retail outlets.

The Oregon Health Authority, which oversees the medical marijuana program, is charged with drafting rules for the new registry. State officials said the agency is still working out how the process will proceed.

Kitzhaber said he shares some of the concerns expressed by opponents of the bill, but noted that the legislation gives power to the health authority to audit financial records of the dispensaries.

"I believe it will be critical to set fees for dispensaries that will provide sufficient funding to OHA so that they can be extraordinarily vigorous in their enforcement of the rules that are developed," he said in his signing letter.